The region of the human papovavirus BK, which corresponds to the early gene control region of SV40, includes a triplication of 68bp which may function in a way similar to the "activator" 72 bp repeats in SV40. To test their activating potential, the BKV repeats have been subcloned and are currently being tested for their activity in several systems available in this laboratory. A possible role of the repeats in determining the host range of the virus will be tested in human, monkey or mouse cells. Also, using the BKV 68 bp repeat region as a probe, experiments are in progress to isolate structurally similar sequences from a human genomic library.